MELK expression in breast cancer is associated with infiltration of immune cell and pathological compete response (pCR) after neoadjuvant chemotherapy.

In experimental settings, maternal embryonic leucine zipper kinase (MELK), an apical member of the snf1/AMPK serine-threonine kinases family, plays a role in tumor growth. We investigated the clinical relevance of MELK expression by performing silico analyses of 7,135 breast cancer patients using multiple independent large cohorts. In triple negative breast cancer (TNBC) found that elevated MELK expression significantly correlates with Nottingham histologic grade and tumor growth according to American Joint Committee Cancer (AJCC) stage. High MELK tumor enriched cell proliferation-related gene sets as well as DNA repair, unfolded protein response, and MTORC signaling gene sets. In two independent cohorts a high mutation rate and worse survival was significantly associated with high MELK tumor. In immune-related gene sets including, allograft rejection, interferon (IFN)-α response, and IFN-γ response, high MELK tumor significantly enriched. Pro-cancer regulatory T cells, T helper type 2 cells and anti-cancer immune cells including CD4+ memory T cells, T helper type1 cells, CD8+ T cells, M1 macrophages, gamma-delta T cells, and dendritic cells with high levels of cytolytic activity (CYT) were highly infiltrated. MELK expression did not correlate with the responses to any of the drugs tested in cell lines. However, pathologic complete response was significantly associated with high MELK following NAC in both TNBC and ER-positive plus HER2-negative breast cancer. In conclusion, cell proliferation, immune response, and NAC breast cancer response was associated with MELK expression. AJCR